During small incision surgery, and particularly during ophthalmic surgery, small probes are inserted into the operative site to cut, remove, or otherwise manipulate tissue. During these surgical procedures, fluid is typically infused into the eye, and the infusion fluid and tissue are aspirated from the surgical site. The aspirated fluids from the surgical site are at least partially drawn into an aspiration chamber located within a surgical cassette. The level of aspirated fluids in the aspiration chamber is measured using a non-invasive level sensor. In prior systems, gas and debris in the aspirated fluids enter the aspiration chamber, which results in the level sensor producing inaccurate readings. This can cause certain problems. Therefore, a need continues to exist for an improved aspiration cassette with gas and debris management.